I'm not sure......but here's what I think.....
I think that when Hawkins uses his power he has to sap his enviroment.
For instance, saving that cat and such might have been responsible for his mother's slow agonizing death. I think in the scene where he sits in the floor and cries in his mother's room they were trying to show the guilt he must have felt for being responsible for the illness and the helplessness of not being allowed to save her.
Same way with the girl. In order to help her he had to draw on the "energy" of the enviroment that's why it seemed to wilt away....
Of course, I could be completely wrong and have no friggin' clue what I'm talking about, so take that with whatever sense your momma gave you
